Whenever you enter a web address (or URL) in a cell, Excel automatically turns that address into a clickable hyperlink.  Excel does the same for network addresses.  Sometimes, that is helpful.  Other times, it can be annoying.

If you find that it annoys more than it helps, you can configure Excel to not turn the text into hyperlinks automatically.  To do that:

1. In Excel 2007, go to the Office button, and click on Excel Options.  See the screenshot below.  In Excel 2010, go to the File menu, and click on Options.

2. In Excel Options, click on Proofing in the left column.  Then, click on the AutoCorrect Options button.

3. In the AutoCorrect Options box, click on the AutoFormat As You Type tab.  Then, uncheck the box next to Internet and network paths with hyperlinks.

4. Click OK twice to return to Excel.

If you find you need to hyperlink text later, you can select the cell, then go to the Insert menu, and choose Hyperlink.  You can also use the keyboard shortcut Ctrl + K to do the same thing.  In the Address field at the bottom, type in the web address.  Press OK.